There have been numerous attempts to create a golf club putter which provides a high accuracy with each putting stroke. Generally, a golf putter club has a centrally-located point of desired contact on the club head (sometimes called the strike point, sweet spot or impact spot), a specific location for the club head's center of gravity, which club head center of gravity often has no relation whatsoever to the impact spot, as well as a specific location for the entire club's center of gravity (occurring after the shaft and grip have been affixed to the club head).
In many prior putters, the club's axis of rotation, i.e., the club's Z axis, is not coaxially aligned with the club face's strike point in the direction of putter stroke movement. Therefore, even if a golfer hits what appears to be a "center hit" ball, because the axis of rotation, i.e., plane containing the entire golf putter's center of gravity, is offset from the club face's strike point, some amount of angular acceleration is undesirably imparted to the ball. This affects the ball's accuracy in terms of direction and speed.
One known putter is of the so-called face-balanced design where the putter head's strike point is aligned offset of the club head's axis of rotation in a plane forward of the face. The name "face balanced" derives from when such a club is laid horizontal on a table surface, with the club head hanging over the edge of the table and allowed to freely rotate about the shaft, the club head face will come to rest aligned horizontally with the table surface and facing up. However, the disadvantage with such putters is that there are inherent forces tending to twist the face open before impact. This is due to the fact that the entire club's axis of rotation is offset forward of the club head's strike point. As a result, the golfer is not assured that the putter head will be perpendicular, i.e., square, to the intended line of club head travel at impact causing misdirection in putting, so a golfer must necessarily use his skill and abilities to overcome such inherent twisting forces. Examples of such face-balanced putters are typified by U.S. Pat. Nos. 4,325,553 and 4,722,528. (The present FIG. 15 depicts the typical offset--labelled "O.S."--of a prior art face-balanced putter's club head's center of gravity relative to the shaft axis.)
Yet another known putter is of the so-called table-balanced design, the head of which, when the putter is laid upon a horizontal table surface with the club head hanging freely beyond the edge, will come to rest with the putter's striking face aligned vertically, rather than horizontally as with the face-balanced design. However, the disadvantage with such a putter design is that there are inherent forces tending to twist the face open at impact, i.e., angular acceleration. This is due to the fact that the entire club's axis of rotation bisects the club head at a point different from the club head's strike point. That is, the plane containing the entire club's center of gravity, i.e., club's axis of rotation, is not aligned with the same vertical plane as the putter's strike point, but instead will be located towards the club head's toe or heel. As a result of this, the golfer is assured that the putter face will return back to square, i.e., perpendicular to the intended line of club head travel. However, because of that misalignment of the entire club's axis of rotation relative to strike point, dynamic forces at impact cause the putter head to rotate closed, i.e., angular acceleration is present. The net result of such twisting is that the golf ball will be caused to travel to the left for a right-handed golfer. Examples of such table-balanced putters are typified by U.S. Pat. Nos. 4,165,554 and 4,852,879. (The present FIG. 16 depicts the typical offset distance--labelled "d"--of a prior art table-balanced putter's club head's center of gravity relative to the shaft axis.)
Many prior putters used a lightweight material (such as aluminum, for example) for the main putter body, and then tried to create a higher moment of inertia by adding a heavyweight material (such as lead or brass, for example) to the toe and heel areas.
No one prior putter simultaneously provides the desired goals of eliminating the known putters' tendency to twist during pendulum-swinging and at impact (due to static and dynamic forces), and achieving a high moment of inertia such that if a golf ball is hit off-center, the club head will nevertheless tend to resist undue twisting thereby minimizing any unwanted angular acceleration imparted to the golf ball.